Treatment of rosin with an aryl thiol

ABSTRACT

ROSIN IS DISPROPORTIONATED AND BLEACHED BY HEATING AT TEMPERATURES OF ABOUT 180-350*C., AND FOR A TIME SUFFICIENT TO REDUCE THE ABIETIC ACID CONTENT TO LESS THAN 15%, IN THE PRESENCE OF 0.01-1% OF AN ARYLTHIOL.

nited States U.S. Cl. 26098 Int. Cl. C09f 1/04 8 Claims ABSTRACT OF THE DISCLOSURE Rosin is disproportionated and bleached by heating at temperatures of about 180-350 C., and for a time sufficient to reduce the abietic acid content to less than 15%, in the presence of 0.01-1% of an arylthiol.

This application is a continuation-in-part of copending application Ser. No. 827,174, filed May 23, 1969, now abandoned.

This invention relates to the simultaneous bleaching and disproportionation of rosin.

The term rosin, as used herein, includes tall oil rosin, wood rosin, gum rosin, crude materials and mixtures containing any of the foregoing, and, in general, any materials containing abietic acid, including tall oil fractions containing various proportions of rosin and fatty acids.

Rosin soap is a preferred emulsifier in rubber polymerization processes. In this application particularly, it is important that the rosin to be used first be stabilized, i.e. rendered less sensitive to oxidation, by conversion of most of the conjugated rosin acids as typified by abietic acid contained therein to an isomer without conjugated double bonds, such as, for example, dehydroabietic acid. This is commonly done by disproportionation, a term used in the art to describe displacement of hydrogen atoms in the abietic acid molecule.

It is known in the art that rosin can be disproportionated by heating it at elevated temperature in the presence of catalysts. Typically, U.S. Pat. 3,277,072 (Patrick and Bestul) teaches the use of iodine, while others (U.S. Pats. 2,130,997; 2,239,555; 2,138,183; 2,154,629;

2,486,183 and 2,580,496) teach the use of noble metals, "such as platinum'or palladium. U.S. Pats. 2,503,268 and 2,497,882 suggest the use of sulfur or selenium. These treatments, however, result only in disproportionation. The treated rosin not only is not bleached, but may actually darken as the result of heating for prolonged periods at high temperatures. Furthermore, additional expenses are inherent in these processes; substantial quantities of additive are required except in the case of the noble metal catalysts and their use, in turn, leads to loss of rosin during filtration. More recently, McBride and Wheelus U.S. Pat. 3,377,334 teaches disproportionation and bleaching by use of 'hydroxylated arylsulfides. While the catalysts of U.S. Pat. 3,377,334 suit their purpose admirably, their preparation is fairly difiicult and comprises many steps.

It is an object of this invention to provide a process for the disproportionation and bleaching of rosin. It is a further object to provide a process not requiring removal of the disproportionating and bleaching agent from the treated rosin. Another object is to provide a class of treating agents having a high degree of activity, yet being readily and economically prepared. Yet another object is to provide rosin having a substantially reduced content of conjugated unsaturated acids of the non-benzenoid type, particularly abietic acid. A further object still is to provide treating agents which will not only disproporatent "ice 3,649,612 Patented Mar. 14, 1972 tionate rosin, but will also markedly lower the softening point of the product.

These and other objects, features, and advantages of this invention will become apparent as the description thereof proceeds.

In accordance with the present invention, it has now been found that these objects can be achieved by a disproportionation process which comprises heating rosin in the presence of a small but effective amount of a particular treating agent.

The treating agents are aryl thiols which may be represented by the general formula:

R2 where:

A represents an aromatic hydrocarbon nucleus including monoand polycyclic aromatic hydrocarbons;

x is an integer from 0 to 3;

y is an integer from 1 to 3;

z is an integer from 0 to 3;

where the sum of x, y and z is not greater than 6 for monocyclic aromatics; and advantageously, polycyclic aromatic hydrocarbons may be used having up to about 18 carbon atoms in the aromatic rings. However, the invention need not be confined to these.

R is a hydrocarbon group, e.g. alkyl, cycloalkyl, and aryl, or suitable substituted alkyl, cycloalkyl, and aryl R desirably contains from 1 to 22 carbon atoms inclusive. Preferred alkyl groups are those containing up to 8 carbon atoms inclusive. Preferred aryl groups are those containing 6 to 18 carbon atoms inclusive, typically phenyl, naphthyl, and anthracyl. Typical cycloalkyl groups contain 3 to 8 carbon atoms in the ring, e.g. cyclopropyl, cyclopropyl, cyclopentyl, and cyclohexyl. Alternatively R may also be a carboxylic acid, halogen, nitro, or amino group.

The terms treating agent or disproportionating agents, as used herein, are defined by Formulas I and II above.

Typical and non-limiting examples of such treating agents are the following: 2-hydroxy-l-mercaptonaphthalene 2,4-dihydroxythiophenol Toluene-3,4-dithiol Thiosalicylic acid 4nonyl-1,2-benzenedithiol 4-chlorothiophen0l Thiophenol 2-aminothiophenol 4-aminothiophenol 4-bromothiophenol 4-tertiarybutylthiophenol 4-nitrothiophenol Ortho-thiocresol Meta-thiocresol Para-thiocresol The conditions for disproportionation and bleaching will vary depending on the starting rosin material and the degree of disproportionation desired. Tall oil rosin is eifectively disproportionated by heating the rosin in the presence of the treating compound at from about 180 C. to 350 C. for from about 1 to 8 hours, wherein the longer times correspond to lower treating temperature and vice versa. Preferred ranges are from about 250 C. to 300 C. for from about 3 to 6 hours.

The degree of disproportionation may be controlled as desired and as dictated by the degree of stability required in the end use. Generally, the abietic acid content should be reduced to less than about by weight of the rosin and preferably to the more commercially acceptable level of less than about 5%, same basis. Reduction of abietic acid content can be followed during the reaction by sampling and analysis, employing any of the procedures known in the art such as the Rubber Reserve (ultraviolet) method (as disclosed in US. Pat. No. 3,377,334) or, preferably by gas-liquid chromatography.

Sequence of admixture of the rosin or rosin mixture with the treating agent is not critical. Likewise, the rosin may be heated to the desired temperature before the treating compound is added or rosin and additive may be first admixed, followed by heating. The process may be conducted at atmospheric, subatmospheric or superatmospheric pressures with corresponding variation in temperature and time of reaction. Also, the process may be carried out on batch, semi-continuous, or continuous basis. The disproportionation is ordinarily conducted under a blanket of inert gas, such as nitrogen, carbon dioxide,

active treating agent of this invention. Tall oil rosin, 500 parts, was charged to a glass reactor fitted with stirrer, thermometer, and inert gas inlet. 2,4-dihydroxythiophenol, 1 part, was added, and the mixture was heated under steam for five hours at 275 C. Samples were withdrawn at 0, l, 3, and 5 hours an analyzed.

The results so obtained are shown in Table II. They show that disproportionation is substantially complete after 3 hours.

EXAMPLE III To show that a catalyst of the type described by the present invention is eifective in disproportionating and bleaching various types of rosin, tall oil rosin, as defined hereinbefore, wood rosin, and gum rosin were treated as in Example II above, using Z-hydroxy-l-naphthaleuethiol as the disproportionating agent. The results are shown in Table III. This table shows that the compounds of the present invention are effective without regard to the type of rosin used. Analyses were carried out by gas-liquid chromatography.

EXAMPLE IV To demonstrate the efliciency of a thiophenol in catalyzing disproportionation at temperatures lower than 290- 320 C., Z-hydroxy-l-naphthalenethiol was used to disproportionate a standard rosin at 225 C. The gradual loss of abietic acid and the formation of dehydroabietic acid is listed below as observed at regular intervals. The lack of decarboxylation is noted by the constant acid number. See Table IV.

steam, and the like. TABLE I Dehydro- The following examples further 1llustrate the 1nven- Abieuc abiefic softemng tron but are not limitatlve thereof except as indicated 1n c 0 1 the appended claims Treating agent percent percent Color degrees Toluene-3,4-dithiol 4. 8 44. 2 WG 67. 0 Thiosalicylie acid 6. l 40. 7 Wt} 64. 5 EXAMPLE I ZA-dihydroxythiophenol 0.6 46.0 K 61.0 Feed (for comparison) 33. 6 21.2 N 81. 0 To compare the disproportionation activity of three 1Ri ns i i t substituted arylthiols, the following experlments were carried out in sealed vessels under identical conditions. The TABLE H rosin used was tall oil rosin conforming to the Naval Dehydro- Stores Act (Feb. 8, 1952 and Federal Specification 235 2355 Add LLL-R-6266, Class C (May 27, 1957), except for less p hours percent percent Color Numb r bottoms content. 3 21,9 N m Rosin, 100 parts, water, 3 parts, and treating agent, 2% 2% 5% lg; 0.1, all parts by weight, were charged to the reaction 1 WG 164 vessel which was then sealed and heated at 290 C. for

TABLE I11 Dehydra- Treating Abiet-ie abietie Temp., agent, Time, acid, acid,

0 percent hours percent percent Color Tall oil rosin. 290 0.1 0 34.7 21.4 N 1 6.2 36.3 X 2 2.3 41.7 X 5 0.3 43.3 WG

Wood rosin 1. 300 0.1 0 39.6 7.9 M 1 4.8 39.8 X 3 1.3 44.1 wW-X 5 0.8 44.8 WGN Gum rosin 300 0.1 0 25.0 6.0 K

1 5.6 41.3 WG a 2.1 43.8 WG-N 5 0.7 45.4 N

three hours. It was then cooled and opened, and the T ABLE W product was removed and analyzed. The data so obtained Tam C natal St cone 0 are shown in Table I. They show effective disproportionap y tion. Abietic and dehydroabietic acid content was de- Ammo g' gg termined by gas-liquid chromatography. The colors are acl acid, Acid based on the conventional US. Department of Agriculture Percent Percent number rosin scale. 911. 0" 34.8 21.5 170.5

ime ours EXAMPLE II 1. 0 16.8 26.7 171.5

a. 5 20. a 171. 8 The purpose of this experlment was to demonstrate the 8-- 3'3 progressive disproportionation of rosin by means of an The softness of the final rosin was noted by its ring and ball softening point of 57 C. The feed rosin had a ring and ball softening point of 81 C.

EXAMPLE V To demonstrate and compare the catalytic activity of two substituted thiophenols of the present invention versus that of 4,4 thiobis(resorcinol), as used in US. Pat. No. 3,377,334, the following catalysts were employed with a standard rosin in sealed reaction vessels, in 0.1% concentration at 290 C. for 2.0 hours (gasliquid chromatography analyses were carried out on the treated rosin). The results are shown in Table V.

TABLE V Dehydra- Abietic abietic Softening acid, acid, pint,

percent percent degrees Feed 34. O 21. 4 81 4,4-thiobis(resorcinol) 4. 2 42. 0 64 2,4-dihydroxythi0phenol 2. 0 42. 2 60 2-hydroxy-l-naphthalenethiol 2. 3 41 7 58 1 Ring and Ball Softening Point.

EXAMPLE VI TABLE VII Hours Analysis Feed 1. 0 3. 0 5. 0

Olelc Acid, percent 23. 2 32. 4 33. 7 34.1 Linoleie acid:

Conjugated, percent 7. 4 11. 3 10. 7 9. 2

Non-conjugated, percent--- 21. 2 5. 8 3. 9 2. 8 Abietie acid, percent 15. 4 0.3 O. 4 0. 3 Dehydroabietic acid, percent 9. 8 23. 9 23. 23. 9

What is claimed is: 1. A method of treating a rosin which comprises heat ing said rosin at a temperature of from about 180 C.

to 350 C. in the presence of from about 0.01% to 1% by Weight of said rosin of an arylthiol compound of the formula:

wherein:

A represents an aromatic hydrocarbon group; x is an integer from 0 to 3; y is an integer from 1 to 3; z is an integer from 0 to 3; the sum of said x, y and z being not greater than 6; and R is selected from the group consisting of a hydrocarbon group having from 1 to 22 carbon atoms, a carboxylic acid group, a halogen, a nitro group, and amino group. 2. The method of claim 1 wherein said R is an alkyl group with up to 8 carbon atoms.

3. The method of claim 1 wherein said R is an aryl group with 6 to 18 carbon atoms.

4. The method of claim 1 wherein said R is a cycloalkyl group with from about 3 to 8 carbon atoms.

'5. The method of claim 1 wherein said arylthiol is 2-hydroxy-l-naphthalenethiol.

6. The method of claim 1 wherein said arylthiol is toluene-3,4-dithiol.

7. The method of claim 1 wherein said arylthiol is thiosalicylic acid.

8. The method of claim 1 wherein said arylthiol is 2,4-dihydroxythiophenol.

References Cited UNITED STATES PATENTS 3,277,072 10/1966 Patrick et a1. 26097.5 3,377,334 4/1968 McBride et a1. 260-88 3,417,071 12/1968 Wheelus 260-108 3,423,389 1/ 1969 Wheelus 260-975 DONALD E. CZAJ A, Primary Examiner R. W. GRIFFIN, Assistant Examiner US. Cl. X.R. 26097.5; 108 

